mdshaw HalfDork
5/5/22 4:48 p.m.

We put solar panels on our house,  41 - 350 watt monocrystal panels, 14.5kw system. It was based on the previous year's energy usage. Somehow we are using much less power this year. Duke shows, our useage is @ 30-40% less month to month, whether from grid or generated compared to last year.  We were doing a lot of construction, replaced the air con system to much bigger 5 ton high sear unit, changed all lights to led, lightening blew up the plasma tv so now it's oled, added a pellet stove so less furnace use & when we did the solar system, I disassembled the entire power panel & tightened all circuit breaker connections & replaced some, some were scary loose. The air con & fau were all 40 years old.
Anyway I can't believe all these translate to a power reduction of this amount.  
So now the point is that we are generating an extra @ 1,000kwh (1Mwh) of power per month for the last 2 months. We will use more power when we use the air con more but not that much. 
The solar panels generate so much power that the microinverters clip the power in the middle of the day. Duke has a minimum $30/month billing so that's what we pay. We get credit for grid power added but at this rate we'll never recoupe that. We don't have batteries & the microinverters need grid power to run so until I figure a way around that or get a ton of battery storage, we'll be on grid. 
So I'm trying to think of a way to use the power in a useful way during the day.  
First idea is to add an EV charger for our Airbnb RV for guests to use.  (Even right now with house ac & rv ac running, the power is about even, just a bit coming from grid.)  As far as I have researched I could add a 40 amp Level 2 charger with a  nema 14-50 plug (or others).  But this wouldn't work with Tesla right? So I would need the normal ev to Tesla adapter or do Tesla owners already have this adapter just in case?

ProDarwin MegaDork
5/5/22 4:51 p.m.

I'm a bit confused... how much do they pay you for extra power generated?  If they pay market rate, there is no more "useful" thing you can do than sell it back to the grid.

adam525i Dork
5/5/22 5:00 p.m.

I'm guessing he gets credit for the extra kWh's he sends there way that he can then use in the following rolling year but doesn't actually get paid for the extra. 

If that is the case, is mining computer money still a thing? EV car would be great if that is something you were already considering. Hot tub or Sauna? Convert appliances from gas to electric?

Keith Tanner
Keith Tanner MegaDork
5/5/22 5:01 p.m.

Have you been through a full year yet? We're overproducing like crazy right now, but I know the shop AC will eat that up when the heat hits based on what I've seen of the bills. I'm hoping to come out 10% ahead at the end of the year. I'll bet that construction was your main consumer last year, though.

I'm coming across the clipping problem as well, interesting.

The EV charging is a great idea if you're running Airbnb, that's a big value add that should let you charge more. Put in a Level 2 with the standard j1772 connector. Teslas come with an adapter to use it. You might want to get your hands on one for forgetful Tesla owners, they're $50.

Cryto mining is a way to burn up energy, but there has to be a better option to do something useful. Maybe you can start producing hydrogen :)


mdshaw HalfDork
5/5/22 7:45 p.m.

In reply to ProDarwin :

Duke credits us for the power added to grid but it's only like 20% or something.  We're 100% ahead since it's been producing in December. 
I thought the Enphase  graphing S/W had an issue with showing the clipping but it's due to the microinverters can only output @250VA & the panels already are providing more to them than they can output mid-day.
Solar sites say it's rare but so far almost everyday it clips the peaks from 11am to 3pm.  I think some of it is the roof slope also, it's only 2/12 so it gets sunlight late into the afternoon.
So the ev charger looks to be a good idea after all.  So get a J1772 charger & the Tesla My wife thinks- great another crazy project. 

Erich UberDork
5/5/22 7:59 p.m.

How do you heat your home? If you switch from a gas furnace to an air source or geothermal heat pump that'll increase your electricity usage. Switch to an electric clothes dryer if you aren't using one already. Switch from a gas stove to electric, or better yet, Induction. 


The EV charger would work too if it gets regular use, but a new EV is more money than all the other things I listed put together. 

mdshaw HalfDork
5/5/22 9:56 p.m.

Everything in our house is electric. I installed a really nice used pellet stove for heat last winter so don't use the furnace for heat any more. The room fan was really noisy & used lots of power. I put an inline 6" vent fan up in the huge chimney chamber that was empty because the 3" pellet chimney goes right past it & ties to a new 6" SS pipe. Anyway it's silent now & uses 75% less power.
Was considering installing a timer for the water heater also to only heat during the day at peak solar time but not sure if my wife & daughter would agree.  
The EV charger would be only for Airbnb guests. Looks like Airbnb has a search feature so all of these Georgia tourists  could charge their EV.

adam525i Dork
5/5/22 10:26 p.m.

Clipping is expected and not a problem with a properly sized solar system. Likely you're limited to 10kW AC output with your utility but with the low cost of modules and inverters typically being good with a 1.5 oversize it makes sense to max them out (14.5 kW DC in your case). That way your 10kW system actually outputs 10kW for longer throughout the day giving you a better payback on the system (provided you use the power and don't give it away!). 

Keith Tanner
Keith Tanner MegaDork
5/5/22 10:37 p.m.

The problem with my array is insufficient wire gauge on the cable leading from the shop (with the array) to the house. It's causing the voltage to rise in the shop and that's causing micros to shut down. We're going to change out that cable. So I'd check to see if there's something restricting your ability to deliver power to the grid. 

Here's the Tesla adapter - like I said, all Teslas come with one but a better host has a spare :)

mdshaw HalfDork
5/8/22 2:11 p.m.

Update on the excess power. Apparently Duke has to buy back the excess power annually. 
They are currently fighting it in Florida & North Carolina state government. They are trying to convince state governments that the excess power that is being generated by solar panels is costing non-solar customers money. 

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